Commonly assigned U.S. Pat. No. 5,316,668 to Tang discloses a wastewater treatment plant comprising a pretreatment chamber, aeration chamber and a settling chamber designed to minimize or eliminate sludge buildup at the bottom of the aeration chamber. Two support walls are provided. The combined function of one support wall and an angular portion at the bottom of the common wall between the aeration and settling chamber is to regulate the flow pattern in the aeration chamber and return settled biodegradable matter from the bottom of the settling chamber to the aeration chamber for further treatment. The fluid flow created by the wall structure enhances the action of the settling chamber and eliminates dead zones in the aeration chamber thus minimizing sludge buildup.
Commonly assigned U.S. Pat. No. 5,484,524 to MacLaren et al. discloses a similar wastewater treatment plant for removal of organic matter, suspended solids and other pollutants comprising a pre-treatment chamber, a biofilm-aeration chamber and a settling chamber. Biofilm grows on biofilm support structure that is stationary and submerged in the mixed liquor of the biofilm aeration chamber. The combination of submerged or surface aeration and suspended solids particle size reduction occurs thereby creating a sufficient fluid flow within the biofilm aeration chamber. This combination of sufficient fluid flow, and reduced size suspended organic particles results in the efficient digestion of organic matter and pollutants by the biofilm growing on the biofilm support structure submerged in the biofilm aeration chamber. This results in a vastly more effective digestive process than conventional processes producing no sludge. Further, resulting treated effluent has a high dissolved oxygen content and low biochemical oxygen demand (BOD) and suspended solids (SS).
This type of treatment system provides effective wastewater treatment before effluent is discharged to an appropriate disposal area. In many parts of the country, disinfected effluent is discharged directly to open drainage ditches or streams. For example, the JET series 1500 treatment system, available from JET Inc. of 750 Alpha Dr. Cleveland, Ohio, has been rigorously tested by the National Sanitation Foundation. The system achieves NSF 40 Class 1 effluent quality, i.e., an effluent quality consistently better than 30 mg/L BOD and 30 mg/L TSS. In Massachusetts, the system is approved for use to repair failed or failing septic systems. The remedial use permit allows certain reductions of Title 5 leaching area requirements. This system is particularly well suited for use where small lots, high groundwater, and/or poor soils are encountered and is currently undergoing pilot testing and achieves some nitrogen and phosphorus removal.
In operation, the system utilizes a motor driven aspirator shaft that thoroughly mixes and disperses fine air bubbles into the aerobic chamber of the treatment tank. This is an activated sludge system, which uses both suspended and fixed growth bacteria to achieve secondary biological treatment. The aeration chamber capacity of 650 gallons for the above-mentioned JET system allows a detention time of more than 30 hours at design flow of 500 gallons per day. Larger systems can handle higher flows. The benefits of such systems include: superior effluent quality, dramatically reduced need for further wastewater treatment; reduced leaching area, or direct effluent discharge after disinfection; decreased separation to groundwater; effective use of poor soil conditions; and increased the life expectancy of the leach area due to discharge of high quality effluent.
Commonly assigned U.S. Pat. No. 5,599,452 to MacLaren et al. discloses another wastewater treatment system that relies on aeration.
U.S. Pat. No. 5,667,689 to Graves discloses a wastewater treatment apparatus that includes at least an aeration chamber and a clarification chamber having a common wall therebetween, a transfer port opening through the common wall between a lower portion of the clarification chamber and the aeration chamber, an aerator mechanism in the aeration chamber for creating wastewater flow currents which flow through an inlet portion of a flow augmenting device located in the common wall above the transfer port. The flow augmenting device is a conduit or pipe having a discharge outlet adjacent the lower portion of the clarification chamber through which exits the flow from the aeration chamber resulting in solid particles being agitated and returned from the clarification chamber lower portion into the aeration chamber through the transfer port. It uses a conventional aerator design.
U.S. Pat. No. 4,608,157 to Graves discloses a wastewater treatment plant which includes pretreatment, aeration, final clarification and overflow/backwash chambers adapted to receive a fluid, such as home wastewater, which is to be subjected to extended aeration or aerobic digestion, the aeration chamber including an aerator having a shaft whose lower end is normally received in the fluid which is to be treated, an aerator foam deflector carried by the shaft which under abnormally high fluid levels increases the torque on the shaft and, thus, indicates abnormal operation, the final clarification chamber including a demand use filter, an overflow outlet operative should the filter become disabled, and a backwash nozzle located in the filter by reverse pumping therethrough fluid pumped from the overflow or backwash chamber. It uses a conventional aerator design.
U.S. Pat. No. 4,505,813 to Graves discloses a wastewater treatment plant which includes pretreatment, aeration, final clarification and overflow/backwash chambers adapted to receive a fluid, such as home wastewater, which is to be subjected to extended aeration or aerobic digestion, the aeration chamber including an aerator having a shaft whose lower end is normally received in the fluid which is to be treated, an aerator foam deflector carried by the shaft which under abnormally high fluid levels increases the torque on the shaft and, thus, indicates abnormal operation, the final clarification chamber including a demand use filter, an overflow outlet operative should the filter become disabled, and a backwash nozzle located in the filter by reverse pumping therethrough fluid pumped from the overflow or backwash chamber. It also uses a conventional aerator design.
In these systems, the primary moving part is the motor driven aerator and water damage is the most common cause of aerator repairs. This damage occurs when the water level in the tank rises to a point where it contacts the aerator and occurs most frequently when there is a blockage of the tank outlet.
Although one method to avoid water damage caused by outlet blockage is the installation of an overflow valve, use of these valves is not always possible and, even when used, these valves are subject to blockage and can be overwhelmed by heavy flooding.
FIG. 1 shows a typical aerator design of the prior art. In this system there are multiple locations where leakage can occur. The seal between the top enclosure and the top endbell is a major leak point in this type of aerator. During a flood of the plant, water rises through the aspirator, aspirator shaft and rotor shaft and spills over the top of the rotor shaft. The rubber disk that seals between the top enclosure and the top endbell does not seal around the rotor shaft at location 1. This provides an open path for liquid to run freely into the interior of the motor.
The thru bolts are another leak point in this type of aerator. When liquid rises to the level of the top of the top endbell, liquid would run between the top enclosure and the top endbell and enter the cavities around the thru bolt heads at 2 and drain down into the motor because the seal washers under the screw heads fail to provide an effective seal.
Another leak point 3 is between the endbells and the stator shell. There is no O-ring seal between the endbells and the stator shell. This area is generally assembled by the motor manufacturer and relies on material applied on the rotor shell edges that dries up and becomes a leak point over time.
Yet another leak point is the lower seal. No grease is applied to the lower seal beneath the bottom bearing shortening the seal life. When the seal wears down, as it always will, it will begin to leak air out of the air seal enclosure, negating the diving bell effect and providing another leak point at location 4.
What is needed is a water resistant aerator that resists leaking and water damage, making the aerator longer lasting, less prone to damage from blockage, and more resilient to wet environments.